performance characteristics of-main

CHAPTER ONE

LITERATURE SURVEY

1.1 CLASSIFICATION OF SUBSTATIONS AND SUBSTATION

LAYOUTS

Substations maybe classified according to service,

mounting, function and type of apparatus.

1.1.1 DISTRIBUTION SUBSTATION: These are transforming

stations where voltages are transformed to low values for use by

household and other small power consumers. This system is

generally a four wire 3 - phase system with the Phase - Phase

Voltage at 415V and the Phase - Neutral Voltage at 230V.

1.1.2 INDUSTRIAL SUBSTATION: These substations serve the

needs of consumers who need bulk power, as it is advisable that

they install an individual substation.

1.1.3 POWER FACTOR CORRECTION SUBSTATION: This variation of

substation is used in the control of the transmission line receiving

end voltage and power factor. They have synchronous condensers

and reactors as their major components. These take care of the

large variations in voltage and power factor, which occur because

of the line inductance and capacitance.

1.1.4 FREQUENCY CHANGER SUBSTATION: These substations

convert any frequency to the type that can be utilized. This

substation is found where there are two or more power systems

1

operating at two different frequencies. A typical example is in the

United Kingdom where independent power producers generate

different frequencies from each other and the public utilities. A

frequency changer substation is used when it is required to

connect the systems together.

This kind of substation is not in the country right now but

with the recent government policy on the deregulation of electric

power industry, independent power producers are expected in the

country and this shall give rise to this kind of substation.

1.1.5 OUTDOOR/INDOOR SUBSTATION: Substations can also be

classified according to whether it is outdoor or indoor. The type

chosen depends on choice after a careful consideration of their

respective advantages and disadvantages.

1.2 ADVANTAGES OF OUTDOOR SUBSTATIONS OVER

INDOOR SUBSTATIONS

1. Outdoor substations require less constructional work than the

indoor substation.

2. Less quantity of building materials is needed.

3. The cost of switchgear installation is less.

4. Adequate spacing between two adjoining equipment can be

provided which will reduce the possibility of faults.

5. Erection of switchgear can be completed in a much lesser time.

2

6. The whole equipment can be viewed and this makes fault

location easier.

7. The scheme is easier to extend when needed.

1.3 DISADVANTAGES OF OUTDOOR SUBSTATIONS

1. A much more space is needed for arranging the equipment.

2. Dirt and dust deposits accumulate over the contacts of switches

etc. and thus, the maintenance cost increases.

3. The switching operations become difficult during rainy season

as the chances of current leakages increase.

1.4 TRANSMISSION SUBSTATION: This serves the purpose of

connecting generating stations to the national grid. They serve the

purpose of stepping up the voltage obtained from the generating

stations to higher values so that power can be sent over long

distances across the country.

1.5 11/0.415KV LOCAL SUBSTATION

An 11/0.415KV distribution substation is a local substation

used to feed the L.T lines within the L.T network. The substation

usually consists of a distribution transformer, a feeder pillar and an

3

RMU for supplying voltage. The substation may be fed through an

RMU or through a set of three J&P fuses on the H.T overhead lines.

RMU are used either as sources of supply or as open points or as

the junction points in the H.T network. They may be installed in the

substation or anywhere along the street, but properly earthed

fence shall be made to enclose the substation RMU which is raised

above the ground by the use of plinths.

The local substation is usually a rectangular enclosed area of

3.8m x 2.74m properly fenced and earthed by wire - gauze

reinforced by concrete pillars. An outlet in the form of a door is

provided in the fence. It is normally sited at junctions of two or

more streets and shall be always locked and only authorized

persons are allowed to enter the fenced area. The ground is

covered with gravel to avoid water - logging or accumulation of oil.

This permits any dripping oil from the transformer to sink into the

soil so as not to cause slippery hazard for the personnel working in

the area. Both the transformer and RMU are raised above the

ground by the use of solid concrete plinths of standard dimensions

specified by the authority for the contractors.

The 11KV supply from either a fused RMU or from H.T.

overhead lines through the three J&P fuses goes into the 11KV

primary - side of the distribution transformer (The size of cables

used depends on the capacity of the transformer but usually,

4

35mm2 XLPE cables or 70mm2, 1 - core cables are used as the

droppers for up to 300KVA transformers). At the L.T secondary

side of the transformer, four single - core cables of sizes

depending on the capacity of the transformers are connected by

the use of Raychem.

1.6 POWER ROUTING AND TRANSFORMER LOADING

PRACTICE

A substation supplies a given area and should be located at

or near the load centre of that area. Thismakes the copper losses

in the outgoing feeders or distributors a minimum and will reduce

difficulties due to voltage drop. In practice however, it is usually

impossible to obtain a suitable substation site at precisely the

point required and hence compromise must be struck.

1.7 ESTIMATION OR PREDICTION OF LOAD

Load prediction for an area depends upon the following factors

among others.

a. Nature of the area

b. Population and population density of area

c. Living standards of people in the locality

d. Industrial, commercial and agricultural development of the

area

5

e. Whether the load forecast is for a new town or

reinforcements of existing supply.

Terms that are important in forecasting load are:

(1) Consumer Demand factor (Df) = Maximum Demand Connected Load

Thus a consumer of maximum demand of 400w, but with connected load of 500w has a Df= 400 = 80% 500

(2) Load Factor = Average load Maximum load

Load Factor = Energy consumed during time t hrs Maximum demand in time t hrs

The needs of consumers differ and accordingly they do not

simultaneously impose their respective maximum demands at the

same time on the supply systems. Accordingly, there is diversity in

the occurrence of load. Thus,

Diversity Factor = Sum of individual Maximum Demands Simultaneous maximum demand

Diversity factor can easily be determined from a study of load

curves of consumers or even the load curve of an area or town.

From this, load current and load duration curve can be deduced

6

which becomes very useful for deciding power generation

requirements for the region.

1.8 TYPES OF LOAD

The main types of load are:

(1) Residential or domestic load which consists of, fans, heaters,

kettles, refrigerators, electric cookers, air conditioners, electric

water heaters and various other small appliances.

(2) Commercial loads which include shop lightings, fans, refrigerators,

light and various types of electric appliances used in commerce.

(3)Industrial load: This may include items in (1) and (2) above in

addition to heavy machineries driven by electric motors,

welding plants, electric furnaces.

Industrial loads may further be classified as

(i) Cottage industries 5kw load

(ii) Small scale industries 25kw load

(iii) Medium scale industries 500kw load

(iv) Heavy industries > 500kw load

In 24 hours, industries demand factors remain at about 85%

to 90% whilst load factor is 70% to 80%.

(4) Government load: This includes various kinds of office

equipment.

(5) Municipal load: This includes street lighting, their offices,

water supply, sewage system and drainage pumps.

(6) Irrigation loads for farms

(7) Mining Load (Heavy machinery)

7

(8) Traction load for trains (not available yet in Nigeria except in

moving devices which carry and generate their power

(requirements).

(9) Bulk supply to distribution centers.

(10) Specialised power requirement such as chemical plants,

steel plants, textile mills, paper mills, refineries and

extraction plants may need specific power supply

arrangement.

It is obvious that different types of load at different time may

be supplied by a power system leading to improvement of

individual load factors.

1.9 TRANSFORMER LOADING PRACTICES

Because of the varying load cycle of most transformers, it is

customary to permit loading considerably in excess of the

transformer nameplate rating. There may be limitations on the

transformer imposed by bushings, leads, tap changers, cables,

disconnecting switches, circuit breakers, etc. Good engineering

design however will permit operation without these limitations.

Increase in transformer loading is limited by the effect of

temperature on insulation life. High temperature decreases the

mechanical strength, increases the brittleness of fibrous insulation,

and makes transformer failure increasingly likely even though

dielectric strength of the insulation may not be seriously

decreased. Overloading should be limited then by considering the

effect on insulation life and transformer life. For recurring loads

8

such as the daily load cycles, the transformer would be operated

for normal life expectancy. For emergencies, either planned or

accidental, loading would be based on some percentage cost of

life.

In a typical case for a failure of part of the electrical system,

a 2.5% loss of life per day for a transformer may be acceptable.The following temperatures and load limitations are

generally applied to transformers. The temperature of the top oil

should never exceed 100oC. The maximum hot-spot winding

temperature should not exceed 150oC for 55oC rise transformers or

180oC for 65oC rise transformers. Short-time peak loading for 1/2hr

or more should not exceed 200% rating. At abnormally high

temperatures, it may be necessary to remove some oil in order to

avoid overflow or excessive pressure.

A substation must be designed to be efficient from the

technological point of view.

That is:

(1) It must be able to carry the load imposed upon it without

causing excessive heating in the conductors, the

consequence of which is damage to insulation.

(2) The voltage drop throughout the network must be kept to a

minimum to hold the voltage at the consumers' terminals

within specified limits, whatever the load condition. An

allowable drop of 10% is used.

9

(3) The substation must be designed to provide for continuity of

supply and should a fault occur on the system, power

interruption to individual consumers must be within the

shortest possible time. The system should be as simple to

operate and maintain as possible and losses must be kept at

a minimum. It is also required that routine maintenance

should be carried out without interruption of supply.

This condition involves a certain amount of circuit

duplication. This highlight the features of a perfect system but

the cost will be prohibitive

1.10 COMMON FAULTS IN DISTRIBUTION SYSTEM

Common faults in distribution system can be categorized as listed

below:

1.) Insulation breakdown in cables, transformer windings,

transformer oil, bushings and insulators.

2.) Over - current, earth - fault, short - circuit faults on lines, underground cables,

breakers and associated equipment.

3.) Over voltage, overload and under voltage.

1.11 NECESSITY OF PROTECTIONS IN DISTRIBUTION

SYSTEMSProtection of electrical distribution supply system is highly

necessary and important to:

10

(a) Prevent damages on the equipment within the network and

safety of personnel.

(b) Limit Load losses and prevent instability of the system .

(c) Maintain the continuityof the system for better revenue

generation .

Protection is achieved by means of Protection devices and

Protective relays.

1.12 PROTECTIVE DEVICES

These devices protect electrical equipment physically

against atmospheric and mechanical fault occurrences. They are:

(a)Lightning Arresters or surge diverters-: used to guard the

outdoor equipment against direct and indirect

lightning - strokes by transferring the accumulated

charges directly to the general earth. Lightning

strokes usually result in over voltages in the network.

(b)Arcing - horns-: Used on transformers and H.T. lines to divert

lightning strikes to earth.

(c)Shield - wire-: Used to protect and shield the entire switchyard

equipment against lightning. It is normally installed above

the switchyard or the H.T lines at angles of 30o to the

shielded equipment.

(d) Lightning - Spikes-: Used to absorb lightning charges down to

the general earth instantaneously.

11

(e) Breathers (Silica gel)-: Used on transformers to prevent ingrain

of moisture.

(f) Pressure - relief device-: Used to release excessive gas -

pressure, generated within transformers during faults,

to the atmosphere.

(g) Oil - level indicators-: Used to monitor the level of oil inside

transformer tanks and oil switch - gears for

satisfactory performances.

(h) Bare - conductor fuses-: Used to protect electrical equipment

against excessive fault currents.

(I) HRC fuses-: Used to protect electrical equipment against

excessive fault currents within shorter - time of fault.

(j) CT and VT-: Used to monitor excess current in a feeder or

transformer and converts it to a value for the

operation of the protective relays.

CHAPTER 2

DATA COLLECTED

2.1.0: SUBSTATIONS IN BENIN ENVIRONMENT

2.1.1: UGBOWO 33/11KV INJECTION SUBSTATION

2.1.1.1 SUBSTATION PARAMETERS

LOCATION: BENIN CITY

CAPACITY: 2 X 15MVA

12

SUBSTATION TYPE: OUTDOOR/INDOOR

EARTHING SYSTEM: EFFECTIVELY EARTHED

D C SYSTEM: 110V DC WITH NEGATIVE GROUND

NUMBER OF RADIATING FEEDERS:4

2.1.1.2 LINE PARAMETERS:

LINE LENGTH: 8KM section one, 6KM section two.

Total line length = 14KM

CONDUCTOR TYPE: AAC (ALL ALUMINIUM CONDUCTORS)

CONDUCTOR AREA: 150mm2

LINE IMPEDANCE: (0.0022 +j0.2) Ω/KM

NOMINAL VOLTAGE: 33KV

CONDUCTOR SPACING: 0.7m

RATED LINE CAPACITY: 30MW

2.1.1.2.1 UGBOWO 11KV FEEDER

LINE PARAMETERS

LINE LENGTH: 20.5KM

MAXIMUM LOAD: 350A

TYPE OF LOAD: RESIDENTIAL, SMALL SCALE INDUSTRIES AND

OFFICES.

NOMINAL SENDING END VOLTAGE: 11KV

13

CONDUCTOR TYPE: AAC (All aluminum conductors)

CONDUCTOR CODE: SPARROW

CURRENT CAPACITY: 401.9A

MW CAPACITY: 7.5MW

CROSS SECTIONAL AREA OF CONDUCTOR: 100mm2

LINE IMPEDANCE = (O.0024 + j0.395) Ω/KM TABLE 2.1: OUTAGES RECORDED IN MAY 2007

DATE DURATION REASONS FOR FAILURE LOAD

INTERRUPTED

06-05-

07

1608 –

2110HRS

(302MINS)

FEEDER OFF SEVICE DUE TO POOR

SYSTEM FREQUENCY 296A

07-05-

07

1005 –

1106HRS

(61MINS)

FEEDER OFF SERVICE ON OVER

CURRENT .RAINSTORM WAS

REPORTED DURING TRIPPING.

260A

16- 05-

07

0430 -

0630HRS

(120MINS)


SYSTEM FREQUENCY. 300A

19-05-

07

1000 –

1430HRS

(270MINS)

FEEDER OFF SERVICE BECAUSE of

A BROKEN CROSS ARMS 316A

26-05-

07

1111 –

1508HRS



14

(242MINS)

30-05-

07

1210 –

1808HRS

(352MINS)

FEEDER OFF SERVICE ON

EMERGENCY FOR THE REPAIR OF

THE LINE CIRCUIT BREAKER.

300A

2.1.1.2.2 FEDERAL GOVERNMENT COLLEGE 11KV FEEDER

LINE PARAMETERS

LINE LENGTH: 7KM

MAXIMUM LOAD: 110A

TYPE OF LOAD: RESIDENTIAL AND OFFICES





MW CAPACITY: 7.5MW


LINE IMPEDANCE = (0.0024 + j0.395) Ω/KM

TABLE 2.2: OUTAGES RECORDED IN MAY 2007

DATE DURATION FAILURE

LOAD

INTERRUPTED

1016– FEEDER WAS OFF ON LOAD

SHEDDING DUE TO POOR

15

01- 05-

07

1109HRS

(53MINS)


04-05-

07

2030–

2116HRS

(46MINS)

FEEDER WAS OFF ON LOAD


SYSTEM FREQUENCY.

110A

16-05-

07

1515-

1816HRS

( 181MINS)

FEEDER OFF SERVICE DUE TO

A CUT DOWN WIRE.

106A

19-05-

07

2020-

2310HRS

(170MINS)

FEEDER WAS OFF ON LOAD


SYSTEM FREQUENCY.

99A

26-05-

07

1516 -

1610HRS

(54MINS)

FEEDER WAS OFF SERVICE AS

A RESULT OF A SHATTERED

LIGHTENING ARRESTER.

108A

2.1.1.2.3 EGUADIAEKEN 11KV FEEDER

LINE PARAMETERS

LINE LENGTH: 9.0KM

MAXIMUM LOAD: 180A

TYPE OF LOAD: MIXED


16




MW CAPACITY: 7.5MW




DATE DURATION FAILURE LOAD INTERRUPTED

02-05-07

0600 – 0715HRS(75MINS)

LOAD SHEDDING DUE TO POOR SYSTEM FREQUENCY.

172A

09-05-07

0600-0730HRS(90MINS)


170A

0600 –

17

13-05-07

0730HRS (90MINS)


166A

16-05-07

1400 – 1442HRS(42MINS)

LOAD SHEDDING DUE TO POOR SYSTEM FREQUENCY

150A

19-05-07

2015-2206HRS(111MINS)


180A

20-05-07

0918-1030(72MINS) LOAD SHEDDING DUE TO POOR

SYSTEM FREQUENCY.170A

26-05-07

0948-1030HRS(72MINS)


180A

31-05-07

1950-2130HRS(130MINS)


180A

2.1.1.2.4 USELU 11KV FEEDER

LINE PARAMETERS

LINE LENGTH: 10KM

MAXIMUM LOAD: 350A

TYPE OF LOAD: MIXED



18



MW CAPACITY = 7.5MW





01-05-07

0530-0830HRS

(180MINS)

LOADSHEDDING DUE TO POOR SYSTEM FREQUENCY. 300A

08-05-07

1950-2200HRS

(190MINS)


16- 05-07

1952-2210HRS


19

(132MINS)22-05-

071206-

1515HRS(189MINS)


24-05-07

1414-1906HRS

(308MINS)

FEEDER OFF SERVICE AS A RESULT OF A BROKEN CROSS ARM

219A

28-05-07

0600 – 0815HRS

(135MINS)


2.1.1.3 INCOMING 33KV LINE PARAMETERS

LINE LENGTH: 8KM section one, 6KM section 2.

Total line length = 12KM

CONDUCTOR TYPE: AAC (ALL ALUMINIUM CONDUCTORS)

CONDUCTOR AREA: 150mm2

LINE IMPEDANCE: (0.0022 +j0.2) Ω/KM



RATED LINE CAPACITY: 30MW

2.1.1.4 SWITCHGEAR ARRANGEMENT

20

Figure 2.1 SINGLE LINE DIAGRAM OF UGBOWO INJECTION SUBSTAT MAY 2007

The substation is fed on 33KV via the same line that supplies power to

Guinness injection substation, from where it tees off to Ugbowo.The

33KV line is 12km long and the substation consists of two 15MVA

transformers. It is interesting to note that until the year 2004, the

substation used to be a 33/6.6KV type. The problem of low voltage and

the associated overload led to its upgrade. The incoming 33KV line ends

at Ugbowo substation. The original arrangement is such that the 33KV

line terminates at Okada injection substation. Siluko Injection Substation

is feeding the Army barracks/Okada axes of the network. This is due to the

operational difficulties being encountered by the Authority of PHCN.This

study is based on the present arrangement

21

FIG.2.2: SINGLE LINE DIAGRAM OF POWER FLOW FROM THE 33KV

SOURCE TO UGBOWO INJECTION SUBSTATION AS AT MAY 2007

22

2.1.2 SILUKO 33/11KV INJECTION SUBSTATION



CAPACITY: 2x15MVA


EARTHING SYSTEM: EFFECTIVELY GROUNDED

DC VOLTAGE: 110Vdc

YEAR OF COMMISSIONING: 1976

NUMBER OF RADIATING FEEDERS: FOUR

2.1.2.2 LINE PARAMETERS

2.1.2.2.1 OLIHA 11KV FEEDER

LINE LENTH: 6KM

MAXUMUM LOAD RECORDED: 360A





MW CAPACITY: 7.5MW


23

TABLE 2.5: OUTAGES RECORDED IN MAY

DATE DURATION REASONS FOR FAILURE LOAD LOST

01-05-071830-2030HRS(120MINS) Feeder was off service on load shedding due to poor

system frequency320A

02-05-071006-1209HRS(123mins) Feeder tripped on earth fault. A cut down cable was

amended before restoration308A

02-05-071830-2030HRS(120mins) Feeder off service on load shedding due to

transformer load limitation330A

05-05-071230-1436HRS(126mins) Feeder off service on emergency load shedding due to

transformer load limitation312A

07-05-070630-1016HRS(226mins) Feeder tripped on over current blue phase. A broken

cross arm was replaced before restoration320A

09-05-071045-1845HRS(480mins)

Feeder was off service on over current. Rainstorm was reported during tripping. Broken poles were replaced before restoration

212A

10-05-071010-2010HRS(600mins)

Feeder tripped on overcurrent.Rainstorm was reported during the tripping and broken poles were re-planted before restoration of service.

300A

15-05-071000-1408HRS(248mins) Feeder was off service for the maintenance of circuit

the line SF6 circuit breaker at the substation.200A

19-05-071408-1610HRS(122mins) Loss of the 33KV incomer. This was to enable them

carry out maintenance at the transmission substation.300A

21-05-071616-2010HRS(236mins) Feeder off service on over current. Rainstorm was

reported during tripping.312A

22-05-071930-2030HRS(60mins) 33KV incomer was opened on load shedding at

Transmission end.338A

25-05-071318-1710HRS(232mins) Feeder was opened on load shedding due to poor

generated power.318A

31-05-071414-1508HRS(54mins) Feeder was opened on load shedding due to poor

generated power320A

24

2.1.2.2.2 UPPER SILUKO 11KV FEEDER

LINE LENTH: 8KM

MAXIMUM LOAD: 240A





MW CAPACITY: 7.5MW


TABLE: 2.6 OUTAGES RECORDED ON UPPER SILUKO FEEDER IN MAY 2007

25

DATE DURATION FAILURE LOAD

LOST

01-05-07 1828-2032HRS

(124mins)

Feeder off service due to poor system frequency.

220A

02-05-07 1606-2210HRS

(364mins)

Feeder off service due to poor system frequency 218A

07-05-07 1206hrs(7/5/7)-

1206hrs(10/5/7)

Broken poles. Rainstorm reported during tripping. 200A

19-05-07 1616-2000HRS

(214mns)

Feeder tripped on over current. Rainstorm was

reported during tripping.

218A

22-05-07 1930-2032HRS

(58mins)

Load shedding because of poor generation. 200A

31-05-07 1444-1500HRS

(16mins)

Load shedding because of poor generation. 212A

2.1.2.2.3 EDO TEXTILE MILL 11KV FEEDER

LINE LENTH: 6.1KM

MAXIMUM LOAD: 290A





MW CAPACITY: 7.5MW


26



LOAD

LOST

06- 05-

07

1016-

1515HRS

(299MINS)

Feeder off service on overcurrent.Lightening was

Reported during tripping.

215A

07-05-

07

0906-

1112HRS

(186mins)

Emergency load shedding on poor system

frequency.

200A

7-5-07 1030-

2230HRS

(180mins)

Load shedding on transformer load limitation 268A

10-5-07 1410-

1432HRS

(22mins)

Feeder off service on over current. Rainstorm

reported during tripping.

116A

13-5-07 2020-

2356HRS

(226mins)

Transformer tripped on over current. 210A

15-05-

07

1618-

2015HRS

(237mins)

Feeder off service for the amendment of a broken

cross arm on the 11kv circuit.

200A

18-05-

07

10120-

1418HRS

(248mins)

Load shedding due to transformer load limitation. 219A

19-05-

07

1730-

2230HRS

(300mins)

Load shedding on poor system frequency. 268A

21-05-

07

1616-

2210HRS

(8mins)


27


LOAD

LOST

22-05-

07

0815-

1015HRS

(120mins)


25-05-

07

1930-

2210HRS

(200mins)


26-05-

07

2010-

2018HRS

(8mins)

Feeder off service on over current 196A

30-05-

07

1616-

1840HRS

(134mins)

Feeder off service on over current. Broken cross

arms were replaced before restoration.

200A

31-05-

07

0010-

1008HRS

(542mins)

Feeder tripped on earth fault. Broken cross arms

were replaced before restoration.

218A

2.1.2.2.4 UWELU 11KV FEEDER

LINE LENTH: 8KM

MAXIMUM LOAD: 320A





MW CAPACITY: 7.5MW

28



DATE DURATION FAILURE LOAD LOST

08-05-07 1030-1530HRS

(300MINS)

Load shedding due to low system

frequency.

299A

10-05-07 1410-1440HRS

(30mins)

Feeder tripped on over current.

Rainstorm was reported during trip.

308A

13-05-07 2010-2350HRS

(190mins)

Transformer tripped o overcurrent.The

transformer is suspected to have been

loaded beyond the set point of its

300A

18-05-07 1000-1510HRS

(310mins)

Feeder was opened on load shedding

due to poor system frequency.

312A

22-05-07 1030-1415HRS

(225mins)


due to poor system frequency

300A

25-05-07 1440-1928HRS

(288mins)



333A

26-05-07 2010-2216HRS

(6mins)



316A

29


The substation is fed by a 33KV line that is approximately 32KM in lenth.The

switchgear are arranged such that the 33KV circuit is outdoor while the 11KV is

indoor. Four 11KV feeders radiate from the substation with two on each

transformer. The areas being fed by these feeders consists of residential,

commercial and industrial loads.

Figure 2.3: SINGLE LINE DIAGRAM OF SILUKO SUBSTATION

2.1.3 WELFARE 33/11KV INJECTION SUBSTATION

2.6.1 SUBSTATION PARAMETERS


CAPACITY: 1 X 15MVA, 33/11KV



DC VOLTAGE: 110V dc

30

YEAR OF COMMISSIONING

NUMBER OF RADIATING FEEDERS: TWO


2.1.3.2.1 UPPER SAKPONBA FEEDER

LINE LENGTH: 7KM

MAXIMUM LOAD: 440A





MW CAPACITY: 7.5MW


TABLE 2. 9: OUTAGES RECORDED IN MAY 2007

31

DATE DURATION REASONS FOR FAILURE FAILURE

LOAD

INTERRUPTED

01-05-07 1828-

2932HRS

(124MINS)

LOAD SHEDDING DUE TO POOR

SYSTEM FREQUENCY

400A

02-05-07 1606-

2210HRS

(364MINS)



19-05-07 1616-

2000HRS

(214MINS)



22-05-07 1930-

2032HRS

(58MINS)



23-05-07 1320-

1700HRS

(220MINS)


SYSTEM FREQUENCY

328A

25-05-07 1440-

1500HRS

(16MINS)

LOAD SHEDDING DUE TO POOR SYSTE


SYSTEM FREQUENCY M FREQUENCY

330A

31-05-07 1830-

2030HRS

(120MINS)

BROKEN CROSS ARM ON THE 33KV

LINE.

414A

2.1.3.2.2 ST. SAVIOUR 11KV FEEDER

LINE LENGTH: 3KM

MAXIMUM LOAD: 70A


32




MW CAPACITY: 7.5MW


TABLE 2.10: RECORDED IN MAY 2007


08-05-07 1030-1530HRS

(300MINS)

Load shedding due to low system frequency.299A

10-05-07 1410-1440HRS(30mins)

Feeder tripped on over current. Rainstorm was reported during trip. 308A

13-05-07 2010-2350HRS(190mins)

Transformer tripped on overcurrent.The transformer is suspected to have been loaded beyond the set point of its protective relays.

300A

18-05-07 1000-1510HRS(310mins)

Feeder was opened on load shedding due to poor system frequency. 312A

22-05-07 1030-1415HRS(225mins)

Feeder was opened on load shedding due to poor system frequency 300A

25-05-07 1440-1928HRS(288mins)


26-05-07 2010-2216HRS(6mins)


33


Two 11KV feeders radiate from this substation namely: UPPER SAKPONBA and

ST. SAVIOUR FEEDERS.

Figure 2.4: SINGLE LINE DIAGRAM 0F WELFARE SUBSTATIO

2.1.4 GUINESS 33/11/6.6KV INJECTION SUBSTATION



CAPACITY: 1 X 15 MVA 33/11KV, 1 X 7.5 MVA 33/6.6KV


EARTHING TYPE: EFFECTIVELY EARTHED

D C VOLTAGE: 110V DC WITH NEGATIVE GROUND


34

2.1.4.2.1 NEW BENIN 11 KV FEEDER

LINE LEGTH: 8 KM

MAXIMUM LOAD: 270A

LINE TYPE: OVERHEAD

TYPE OF LOAD: RESIDENTIAL, COMMERCIAL AND COTTAGE

INDUSTRY





MW CAPACITY: 7.5MW


TABLE 2.11: OUTAGES RECORDED IN MAY 2007DATE DURATION FAILURE LOAD

INTERRUPTED10-05-07 0530-0700HRS

(90MINS)FEEDER OFF SERVICE ON POOR SYSTEM FREQUENCY.

120A

16-05-07 1630-1710HRS(40MINS)

FEEDER OFF SERVICE AS ARESULT OF A CUT DOWN 11KV CONDUCTOR.

220A

21-05-07 1515- 1810HRS(175MINS)

FEEDER OFF SERVICE AS A RESULT OF POOR SYSTEM FREQUENCY.

211A

24-05-07 2030-2115HRS(75MINS)

FEEDER OFF SERVICE AS ARESULT OF TRANSFORMER LOAD LIMITATION.

210A

30-05-07 2110-2115HRS (5MINS)

FEEDER TRIPPED ON OVERCURRENT. THUNDERSTORM WAS REPORTED DURING TRIPPING.

215A

2.1.4.2.2 BDPA 11KV FEEDER

35

LINE LENGTH: 4KM

MAXIMUM LOAD: 230A

TYPE OF LOAD: RESIDENTIAL





MW CAPACITY: 7.5MW




01-05-07 0530-0630HRS

(60MINS)

FEEDER OFF SERVICE DUE

TO POOR SYSTEM

FREQUENCY

200A

04-05-07

1016 – 1508HRS

(308MINS)

FEEDER OFF SERVICE AS A

RESULT OF A SHATTERED

LIGTHENING ARRESTER.

216A

10-05-07

1020-1410HRS

(230MINS)


TO BROKEN CROSSARM. 216A

14-05-07

1020-1410HRS

(230MINS)


TO POOR SYSTEM

FREQUENCY.

200A

36


15-05-07

1810-1910HRS

(60MINS)

FEEDER OFF SERVICE FOR

THE EMERGENCY REPAIR

OF A BREAKER

200A

16-05-07

1440-1810HRS

(210MINS)


TO A SHATTERED

LIGHTENING

180A

27-05-07

1106-1206HRS

(60MINS)


LOAD SHEDDING DUE TO

POOR SYSTEM

FREQUENCY.

200A

2.1.4.2.3 ASABA 6.6 KV FEEDER

LINE LENGTH: 7KM

MAXIMUM LOAD: 400A

TYPE OF LOAD: RESIDENTIAL/COTTAGE INDUSTRIES

NOMINAL SENDING END VOLTAGE: 6.6KV



CURRENT CAPACITY: 670A

MW CAPACITY: 7.5MW


LINE IMPEDANCE (0.0024 + j0.395)/KM

37

TABLE 2.2.13: OUTAGES RECORDED IN MAY

DATE DURATION FAILURELOAD INTERRUPTED

01-05-07 0545-0745HRS

(120MINS)

FEEDER TRIPED ON

OVERCURRENT.THE FEEDER WAS

LOADED BEYOUND THE SET

VALUES FOR THE PROTECTIVE

RELAYS.

400A

02-05-07 1016-1208HRS

(112MINS)

FEEDER TRIPED ON

OVERCURRENT.THE FEEDER WAS

LOADED BEYOUND THE SET

VALUES FOR THE PROTECTIVE

RELAYS.

392A

04-05-07 2020-2115HRS

(65MINS)


SYSTEM FREQUENCY

318A

06-05-07 0630-0715HRS

(45MINS)

FEEDER TRIPPED ON OVERCURRENT.

RAINSTORM WAS REPORTED

DURING THE FAILURE 200A

08-05-07 1616-1830HRS

(134MINS)


SYSTEM FREQUENCY.

180A

10-05-07 2008-2116HRS

(68MINS)


FEEDER IS SUSPECTED TO HAVE

BEEN OVERLOADED.

399A

18-05-07 1306-1408HRS

(62MINS)

LOADSHEDDING DUE TO POOR

SYSTEM FREQUENCY.

206A

21-05-07 1108-1208HRS

(60MINS)

FEEDER WAS OFF SERVICE FOR THE

REFIL OF LINE CIRCUIT BREAKER

WITH SF6 GAS. 200A

22-05-07 0630-1118HRS

(288MINS)

FEEDER OFF SERVICE DUE TO POOR


38

24-05-07 1010-1810HRS

(480MINS)

FEEDER TRIPPED ON EARTH FAULT.

A CUT DOWN CONDUCTOR WAS

REPAIRED BEFORE RESTORATION. 200A

26-05-07 1515-1615HRS

(60MINS)

FEEDER WAS OFF SERVICE ON LOAD

SHEDDING DUE TO POOR SYSTEM

FREQUENCY.

119A

28-05-07 2008-2016HRS

(120MINS)


OVERLOAD BEYOUND PROTECTION

SETTING. 399A

31-05-07 0530-0730HRS

(120MINS)


OVERLOAD BEYOUND PROTECTION

SETTING. 390A

2.1.4.3 INCOMING 33KV FEEDER

LINE LENGTH: 8KM

LINE TYPE: OVERHEAD

CONDUCTOR TYPE: AAC

LINE IMPEDANCE :( 0.0022+j0.22)Ω/KM



39


Figure2.5: SINGLE LINE DIAGRAM OF GUINESS SUBSTATION

The substation is fed by a 20KM –long 33KV line from the transmission substation. The

injection substation, which is the indoor/outdoor type, has two power transformers with

different power and voltage ratings.

2.1.5 NEKPENEKPEN 33/11KV INJECTION SUBSTATION



CAPACITY: 2x15MVA



SYSTEM DC VOLTAGE: 110V DC

40


2.1.5.2.1 FEEDER 1

LENTH OF LINE: 7KM

LINE TYPE: OVERHEAD

MAXIMUM LOAD RECORDED: 350A

TYPE OF LOAD: MIXED

TABLE 2.14: OUTAGES RECORDED IN THE MONTH OF MAY


02-05-07

1015-1315HRS(180MINS)

Feeder was off service on load shedding due to poor system frequency 300A

06-05-07

1530-2010HRS(280MINS)

Feeder tripped on over current. Rainstorm was reported during tripping. 295A

09-05-07

0630-1030HRS(280MINS)

Feeder was off service as a result of a broken cross arm. 318A

10-5-7 1620-1830HRS(130MINS)

Feeder was off service for the emergency repair of a hot spot at the 11kv busbar. 326A

16-05-07

1440-1640HRS(120MINS)

Feeder was off service as a result of high transformer winding temperature. 318A

20-05-07

2310-2354HRS(44MINS)

Feeder was off service due to system frequency correction. 341A

41

2.1.5.2.2 FEEDER 2

LENTH OF LINE: 6KM

LINE TYPE: OVERHEAD

MAXIMUM LOAD: 400A

TYPE OF LOAD: RESIDENTIAL, COMMERCIAL AND COTTAGE INDUSTRY





MW CAPACITY: 7.5MW




LOST

5-05-

07

1015-

1035HRS

(20MINS)

Feeder tripped on over current 210A

5-5-07

1902-

2115HRS

(133mins)

Feeder off service due to transformer load

limitation

350A

6-05-

07

0630-

1108HRS

(66mins)

Feeder off service for replacement of broken pin

insulator 320A

12-5-

07

2210-

2315hrs

Feeder tripped on earth fault. Cut down wire was

amended before restoration 316A

42

(65mins)

14-05-

07

1010-

1806HRS

(474mins)

Feeder off service due to broken pole

310A

14-05-

07

1515-

1610hrs

(53mins)

Feeder off service on poor system frequency

312A

16_05-

07

1018-

1316hrs

(178mins)

Feeder off service on over current. A cut down

jumper was replaced before restoration 296A

22-05-

07

1832-

1942hrs

(50mins)

Feeder off service to correct poor system

frequency. 310A

30-05-

07

1916-

2110hrs

(114mins)

Feeder off service on transformer load limitation 382A

31-05-

07

0630-

0710hrs

(40mins)

Feeder tripped on over current 375A

2.1.5.2.3 FEEDER 3

LINE LENTH: 6KM

LINE TYPE: OVERHEAD

MAXIMUM LOAD: 410A

TYPE OF LOAD: MIXED

43


01-05-07 0530-0630HRS

(60MINS)


TO POOR SYSTEM

FREQUENCY

200A

04-05-07

1016 – 1508HRS

(308MINS)

FEEDER OFF SERVICE

BECAUSE of A SHATTERED

LIGTHENING ARRESTER.

216A

10-05-07

1020-1410HRS

(230MINS)


TO BROKEN CROSSARM. 216A

14-05-07

1020-1410HRS

(230MINS)


TO POOR SYSTEM

FREQUENCY.

400A

15-05-07

1810-1910HRS

(60MINS)

FEEDER OFF SERVICE FOR

THE EMERGENCY REPAIR

OF A BREAKER

430A

16-05-07

1440-1810HRS

(210MINS)


TO A SHATTERED

LIGHTENING

380A

27-05-07

1106-1206HRS

(60MINS)



POOR SYSTEM

FREQUENCY.

200A


44

2.1.5.2.4 FEEDER 4

LINE LENGTH: 7.1KM

LINE TYPE: OVERHEAD







MW CAPACITY: 7.5MW



LOST

01-05-07 1816-2000HRS

(104MINS)

Load shedding on poor system

frequency 200A

06-05-07 0016-

0230HRS(134MIN

S)

Feeder off service on over

current.Rainstorm was reported

during tripping.

212A

09-05-07 0630-1030HRS

(240MINS)

Feeder off service on over current. A

broken crosarm was replaced before

restoration.

200A

16-05-07 1500-1606HRS

(126MINS)

Load shedding due to transformer

load limitation. 96A

19-05-07 0816-1016HRS

(120MINS)

Feeder tripped on earth fault. A cut

down conductor was replaced before

restoration.

168A

20-05-07 1616-1630HRS Feeder tripped on over current.

45

(14MINS) Lightening storm was reported

during tripping.

210A

29-05-07 1008-1216HRS

(128MINS)

Feeder off service on over current.

Rainstorm reported during tripping. 200A

TABLE 2.17: OUTAGES RECORDED IN THE MONTH OF MAY 2007


The injection substation fed via Nekpenekpen 33KV feeder from the transmission

substation at Sapele road Benin City. The 33KV switchgear arrangement is outdoor while

the 11KV ones are the indoor type. The substation supplies power to Sakponba,

Evbuoriaria, Oka, Ugbekun, Idogbo and Muritala Mohammed settlements of Benin City.

These are densely populated settlements that consist of mixed loads, as activities ranging

from commercial to private and governmental take place here. Four 11KV feeders radiate

from the substation, two being fed by each of the transformers.

46

Figure 2.6: SINGLE LINE DIAGRAM OF NEKPENEKPEN SUBSTATIO

2.1.6 ETETE 33/11KV INJECTION SUBSTATION



CAPACITY: 2x15MVA


EARTHING SYSTEM: EFFECTIVELY GROUNDED

D C VOLTAGE: 110Vdc WITH NEGATIVE GROUND

YEAR OF COMMISIONING: 1997


47

2.1.6.2.1 IHAMA 11KV FEEDER

LINE LENGTH: 5KM

MAXIMUM LOAD: 432A

TYPE OF LOAD: RESIDENTIAL/GOVERNMENT





MW CAPACITY: 7.5MW




02-05-07

1015-1315HRS(180MINS)


06-05-07

1530-2010HRS(280MINS)


09-05-07

0630-1030HRS(280MINS)

Feeder was off service because of a broken cross arm. 318A

10-5-7 1620-1830HRS(130MINS)


16-05-07

1440-1640HRS

Feeder was off service because of high transformer winding temperature. 388A

48

(120MINS)20-05-07

2310-2354HRS(44MINS)

Feeder was off service due to system frequency correction. 349A

2.1.6.2.2 DUMEZ 11KV FEEDER

LINE LENGTH: 6KM

MAXIMUM LOAD: 264A

TYPE OF LOAD: RESIDENTIAL/OFFOCIAL





MW CAPACITY: 7.5MW



02-05-07

1015-1315HRS(180MINS)


06-05-07

1530-2010HRS(280MINS)


09-05-07

0630-1030HRS(280MINS)

Feeder was off service because of a broken cross arm. 118A

10-5-7 1620-1830HRS(130MINS)


16-05-07

1440-1640HRS(120MINS)

Feeder was off service because of high transformer winding temperature. 188A

20-05- 2310- Feeder was off service due to system frequency

49

07 2354HRS(44MINS)

correction. 229A

TABLE 2.9 : OUTAGES RECORDED

2.1.6.2.3 UGBOR 11 KV FEEDER

LINE LENGTH: 6KM

MAXIMUM LOAD: 440A

TYPE OF LOAD: RESIDENTIAL/OFFICES




MW CAPACITY: 7.5MW


TABLE 2.20: OUTAGES RECORDED IN MAYDATE DURATION FAILURE LOAD

LOST

01-05-07 1816-2000HRS

(104MINS)

Load shedding on poor system

frequency 300A

06-05-07 0016-

0230HRS(134MIN

S)

Feeder off service on over

current.Rainstorm was reported

during tripping.

312A

09-05-07 0630-1030HRS

(240MINS)

Feeder off service on over current. A

broken crosarm was replaced before

restoration.

300A

16-05-07 1500-1606HRS

(126MINS)

Load shedding due to transformer

load limitation. 296A

50

19-05-07 0816-1016HRS

(120MINS)

Feeder tripped on earth fault. A cut

down conductor was replaced before

restoration.

168A

20-05-07 1616-1630HRS

(14MINS)

Feeder tripped on over current.

Lightening storm was reported

during tripping.

310A

29-05-07 1008-1216HRS

(128MINS)

Feeder off service on over current.

Rainstorm reported during tripping. 230A

2.1.6.2.4 UPPER SAPELE 11KV FEEDER

LINE LENGTH: 7KM

MAXIMUM LOAD: 316A

TYPE OF LOAD: RESIDENTIAL AND OFFICIAL


CONDUCTOR TYPE: AAC



MW CAPACITY: 7.5MW


51


DATE DURATION REASONS FOR FAILURE FAILURE LOAD LOST

02-05-07 0530-0730hrs

(120MINS)

Load shedding due to poor system

frequency 300A

04-05-07 1018-1416HRS

(238MINS)

Broken cross arm .Rainstorm as

reported during tripping 309A

06-05-07 2010-2210HRS

(120MINS)


frequency 300A

08-05-07 1944-2210HRS

(86MINS)

Load shedding due to transformer load

limitation. 296A

18-05-07 1614-2018HRS

(244MINS)

Feeder tripped on earth fault. Broken

poles were replaced before restoration. 290A

21-05-07 2014 -2030 HRS

(16MINS)

Feeder tripped on over current. Broken

poles were replaced before restoration. 211

24-05-07 1015-

1206HRS(111MINS)


frequency. 290A

26-05-07 1515-1608HRS

(53MINS)


frequency 310A

27-05-07 0810-0916HRS

(66MINS)


frequency 306A

29-05-07 1018-1416HRS

(238MINS)


frequency 289A

29-05-07 1018-1416HRS

(238MINS)


frequency 289A

31-05-07 1106-1119HRS

(13MINS)


frequency 211A

52


This substation is fed via ETETE 33KV feeder from the transmission substation,

which is just 2.8km away. Four 11KV feeders radiate from the substation with

two tied to each transformer. These feeders are IHAMA, DUMEZ, UGBOR and

UPPER SAPELE 11KVfeeders.

Figure 2.7: SINGLE DIAGRAM OF ETETE INJECTION SUBSTATION

2.1.7 GRA 33/11KV INJECTION SUBSTATION


LOCATION: BENIN CITY, EDO STATE.

CAPACITY: 2x15MVA




DC SYSTEM: 110V DC WITH NEGATIVE GROUND


2.1.7.2.1 OBA PALACE 11KV FEEDER

53


LINE TYPE: OVERHEAD

LINE LENTH: 7KM

TYPE OF LOAD: OFFICES, COTTAGE INDUTRIES AND RESIDENTIAL.

TABLE 2.22 OUTAGES RECORDED IN MAY 2007


LOST

12-15-

07

1006-

1200HRS

(114MINS)

The line was interrupted for replanting of a

broken pole.

280A

22-05-

07

1600-

1200HRS

(55MINS)

The feeder tripped on over current. Rainstorm

was reported during tripping.

252A

54

2.1.7.2.2 GRA 11KV FEEDER


LINE TYPE: OVERHEAD

LINE LENTH: 6KM


DATE DURATION

FAILURE

LOAD LOST

09-05-

07

1616 -1635HRS

(19MINS)

The feeder tripped on earth fault. A cut-down

conductor was amended before restoration.

230A

16-05-

07

0205-0630HRS

(265MINS)

The feeder tripped on over current red and blue

phases. Rainstorm was reported during the trip. 200A

24-05-

07

1935-2000HRS

(25MINS)

The line was of service as the 33KV feeder was

opened on emergency load shedding for system

frequency control.

250A

30-05-

07

1000-1245HRS

(165MINS)

The feeder was opened for the emergency

maintenance of its line breaker, which lost SF6

gas.

270A

30-05-

07

1608-1702HRS

(66MINS)

The feeder tripped on over current blue phase. It

was patrolled and no fault was found .It was

then restored back to service.

258A

55

2.1.7.2.3 RESERVATION 11KV FEEDER

MAXIMUM LOAD: 430A

LINE LENTH: 6KM

TYPE OF LOAD: RESIDENTIAL/GOVERNMENT OFFICES

CONDUCTOR TYPE: AAC

CURRENT RATING: 401.9A

MW RATING: 7.5MW

TABLE 2.24 OUTAGES RECORDED IN MAY


LOAD

LOST

12-5-

07

1440-

1540HRS

(60MINS)

The feeder was opened on emergency to replant

a weak electric pole 398A


56

Figure 2.8: SINGLE LINE DIAGRAM OF GRA SUBSTATION

GRA 33KV feeder feeds the substation from Benin transmission substation at

sapele road in Benin City. The 33KV switchgear arrangement is outdoor and

consists of isolators, circuit breakers, insulation support and surge arresters which

are so arranged that the 33KV line feeds into 33KV busbar to which two

transformers are connected via isolators and circuit breaker.

The 11KV circuit is indoor. The circuit breaker CB4 is provided to facilitate both

parallel operation of the two transformers and to allow for transfer of load from

one transformer to the other. At the time of this research however, the

transformers were running individually and not in parallel.Transfomer one feeds

Oba palace and GRA feeders while transformer 2 feeds Reservation feeder.

57

2.1.8 EVBUOTUBU 33/11KV INJECTION SUBSTATION



CAPACITY: 1 X 15MVA, 33/11KV


DC SYSTEM: 110Vdc WITH NEGATIVE GROUND



2.1.8.2.1 EVBUOTUBU 11KV FEEDER

58

LINE LENGTH: 8KM

MAXIMUM LOAD: 288A


CONDUCTOR TYPE: AAC



MW CAPACITY: 7.5MW




06-05-07 1005-1206HRS

(120MINS)

LOAD SHEDDING DUE TO POOR FREQUENCY 200A

16-05-07 1216- 1416HRS

(120MINS)


22-05-07 0630-1006HRS

(116MINS)


24-05-07 1944-2210HRS

(146MINS)


26-05-07 1515-2010HRS

(295MINS)


30-05-07 0201-0415HRS

(134MINS)


59

2.1.8.2.2 ASORO 11KV FEEDER

LINE LENGTH: 8KM

MAXIMUM LOAD: 255A


CONDUCTOR TYPE: AAC



MW CAPACITY: 7.5MW




09-05-

07

1930-

2230HRS

(180MINS)

LOAD SHEDDING DUE TO POOR SYSTEM

FREQUENCY

250A

19-05-

07

1930-

2230HRS

(180MINS


FREQUENCY

250A

26-05-

07

0530-

0730HRS

(120MINS)


FREQUENCY 250A

28-05-

07

1414-

1814HRS LOAD SHEDDING DUE TO POOR SYSTEM

FREQUENCY

200A

60

(240MINS)

31-05-

07

0530-

0700HRS

(90MINS)


FREQUENCY

250A


Figure 2.9: SINGLE LINE DIAGRAM OF EVBUOTUBU SUBSTATION

The substation is one of the newest in the zone and it supplies power to the Evbuotubu, Ekenwan and Asoro communities. The load is largely residential with pockets of cottage industries. The substation is supplied on 33KV from the transmission substation. Two 11KV feeders are available and they are EVBUOTUBU and ASORO 11KV feeders.

2.1.9 FEDERAL SECRETERIAT 33/11KV INJECTION SUBSTATION



CAPACITY: 1X 15MVA, 33/11KV


EARTHING SYSTEM: EFECTIVELY EARTHED

DC SYSTEM: 110V DC WITH NEGATIVE GROUND

61


2.1.9.2.1 NEW AUCHI 11KV FEEDER

LINE LENGTH: 6KM

MAXIMUM LOAD: 440A


CONDUCTOR TYPE: AAC



MW CAPACITY: 7.5MW




LNTERRUPTED

01-05-07 0630-

0800HRS

(90MINS)


POOR SYSTEM

FREQUENCY

399A

06-05-07 1616-

2016HRS

(240MINS)


POOR SYSTEM

FREQUENCY

409A

16-05-07 1010-

1510HRS

(300MINS)


POOR SYSTEM

FREQUENCY

410A

23-05-07 1606-

1620HRS


POOR SYSTEM 430A

62

(14MINS) FREQUENCY

29-05-07 1930-

2030HRS

(60MINS)


POOR SYSTEM

FREQUENCY

300A

2.1.9.2.2 FEDERAL HOUSING 11KV FEEDER

LINE LENGTH: 4KM

MAXIMUM LOAD: 180A


CONDUCTOR TYPE: AAC



MW CAPACITY: 7.5MW




INTERRUPTED

06-05-

07

0530-

0730HRS

(120MINS)



10-05-

07

0545-

0730HRS

(105MINS)


SYSTEM FREQUENCY

170A

16-05-

07

1930-

2030HRS

(60MINS)



63


Figure 2.10: SINGLE LINE DIAGRAM OF FEDERAL SECRETERIAT SUBSTATION

2.1.10 IKPOBA DAM 33/11KV INJECTION SUBSTATION



CAPACITY: 1X7.5MVA &1X15MVA, 33/11KV



DC VOLTAGE: 110VDC WITH NEGATIVE GROUND.


2.1.10.2.1 DAM 11KV FEEDER

LINE LENGTH: 0.1KM

64

MAXIMUM LOAD: 200A


CONDUCTOR TYPE: AAC



MW CAPACITY: 7.5MW




06-05-07

1440-1630HRS

(110MINS)

FEEDER WAS OFF SERVICE FOR THE MAINTENANCE OF ITS TERMINAL EQUIPMENT

186A

2.1.10.2.2 UPPER LAWANI 11KV FEEDER

LINE LENGTH: 4KM

MAXIMUM LOAD: 110A


CONDUCTOR TYPE: AAC



MW CAPACITY: 7.5MW


TABLE 2.30: OUTEGES RECORDED IN MAY 2007


65

INTERRUPTED06-05-

071440-

1635HRS(115MINS)

GENERAL MAINTENANCE 100A

16-05-07

0650-1005HRS

(255MINS)

POOR SYSTEM FREQUENCY 105A

20-05-07

1005-1210HRS

(125MINS)


22-05-07

1616-1916HRS

(180MINS)


26-05-07

0530-0730HRS

(120MINS)


2.1.10.2.3 OKHORO 11KV FEEDER

LINE LENGTH: 4.5KM

MAXIMUM LOAD: 190A


CONDUCTOR TYPE: AAC



MW CAPACITY: 7.5MW




66

6-05-07 1440-1640HRS

(120MINS)

GENERAL MAINTENANCE 180A

07-05-07 0630-0700HRS

(30MINS)


10-05-07 1630-1930HRS

(180MINS)


13-05-07 1900-2200HRS

(180MINS


23-05-07 2210-2220HRS

(10MINS)


29-05-07 0630-0659HRS

(29MINS)



Figure 2.11: SINGLE LINE DIAGRAM OF IKPOBA DAM SUBSTATION

67

This substation supplies power to Ikpoba River dam which is the only water works in

Benin City and to two other feeders on 11KV .The feeders are: OKHORO &

LAWANI 11KV FEEDERS.

2.2.0 SUBSTATIONS IN DELTA STATE ENVIRONMENT

2.2.1 OGHAREKI 33/11KV INJECTION SUBSTATION


LOCATION: Oghara town Delta state

CAPACITY: 1x15MVA

SUBSTATION TYPE: outdoor/indoor



LINE LENGTH: 10KM

68

LINE TYPE: OVERHEAD

MAXIMUM LOAD RECORDED ON THE FEEDER: 450A

MINIMUM LOAD RECORDED ON THE FEEDER: 215A





MW CAPACITY: 7.5MW




16-05-07

1000-

1015HRS

(15MINS)

LOSS OF SOURCE 300A

22-05 -07

2105-2145HR

(40MINS)

FEEDER TRIPPED ON OVERCURRENT

A BLOWN HRC FUSE WAS REPLACED

BEFORE RESTORATRION

408A

30-05-07

2130-

2155HRS

(25MINS)

FEEDER TRIPPED ON OVERCURRENT

A BLOWN HRC FUSE WAS REPLACED

BEFORE RESTORATRION

430A


69

The substation receives supply from Amukpe 330/33KV transmission substation

via Mosogar 33KV feeder. The 33KV switchgear is outdoor and 11KV

switchgear arranged indoor. One 11KV feeder, Oghareki 11KV feeder originates

from the station. This feeder feeds the Oghareki community, which has mixed

loads (residential, small cottage industries, offices and schools).

2.2.2 OGHAREFE 33/11KV INJECTION SUBSTATION

70


CAPACITY: 1x15MVA




2.2.2.2.1 GOVERNOR 11KV FEEDER

LINE LENTH: 6KM

TYPE OF LINE: OVERHEAD

TYPE OF LOAD: OFFICES, RESIDENTIAL AND COTTAGE INDUSTRIES.






MW CAPACITY: 7.5MW

CROSS SECTIONAL AREA OF CONDUCTOR:100mm2

OUTAGES RECORDED IN THE MONTH OF MAY 2007: NIL

2.2.2.2.2 OTEFE 11KV FEEDER

LINE LENTH: 10KM


TYPE OF LOAD: COTTAGE INDUSTRIES, OFFICES AND RESIDENTIAL.



71




MW CAPACITY: 7.5MW


TABLE 2.33 OUTAGES RECORDED IN THE MONTH OF MAY


6-05-07

0245-1045HRS

(480mins)

Broken pin insulators at Otefe town

caused the trip. 200A

18-5-07

0924-1010HRS

(46mins)

Feeder opened to enable maintenance

crew replace blown HRC fuses. 272A

2.2.3 BETA GLASS 33/11KV INJECTION SUBSTATION


LOCATION: UGHELLI, DELTA STATE

CAPACITY: 1x7.5MVA


YEAR OF FIRST COMMISSIONING: 1978


2.2.3.2.1 UGHELLI 11KV FEEDER

LENTH OF LINE: 12KM

TYPE OF LINE: Overhead

72







MW CAPACITY: 7.5MW


TABLE 2.34: OUTAGES RECORDED ON THE FEEDER IN MAY2007


03-05-07 0600-1035HRS.

(275mins.)

The feeder tripped on earth fault. A tree branch was removed from the line before restoration.

180A

16-05-07 1436-1458HRS.

(22mins.)

There was loss of supply from the source 33kv feeder. This was for the purpose of maintenance of their 33kv line breaker.

200A

26-05-07 2006-2027HRS.The feeder tripped on over current red phase.

200A

73

(21mins.)

2.2.3.2.2 BETA GLASS 11KV FEEDER

LENTH OF LINE=3KM


MAXIMUM LOAD: 150A

TYPE OF LOAD: INDUTRIAL (GLASS FACTORY)





MW CAPACITY: 7.5MW CROSS SECTIONAL AREA OF CONDUCTOR:100mm2



16-05-07

1436-1458(22MINS)

THERE WAS LOSS OF POWER FROM SOURCE 33KV SUBSTATION.

120A


74

Figure2.14: SINGLE LINE DIAGRAM OF BETA GLASS SUBSTATION

The substation, which is both the indoor and outdoor type, is fed via a 2km-long

33kv feeder which comes from Delta power station also in ughelli. The 33kv

switchgear is outdoor while the 11kv switchgear is indoor. The 33kv arrangement

consists of a line isolator, an SF6 gas circuit breaker and a transformer isolator.

The 11kv output of the transformer goes straight to the indoor switchgear

arrangement for distribution to consumers via two 11kv overhead lines.

CHAPTER 3

ANALYSIS OF DATA

3.1.0 SUBSTATIONS IN BENIN ENVIRONMENT

3.1.1 UGBOWO 33/11KV INJECTION SUBSTATION

CALCULATIONS

Current in section 1 = Current due to Ugbowo substation + Current due to

Guinness substation

75

CURRENT DUE TO UGBOWO SUBSTATION

MAXIMUM LOAD DUE TO TRANSFORMER 1= 460A

MAXIMUM LOAD DUE TO TRANSFORMER 2=530A

TOTAL LOAD = 990A AT 11KV

TOTAL LOAD =330A AT 33KV

CURRENT DUE TO GUINESS SUBSTATION

MAXIMUM LOAD DUE TO TRANSFORMER 1 = 500A AT 11KV (166.7A

AT 33KV)

MAXIMUM LOAD DUE TO TRANSFORMER 2 = 400A AT 6.6KV (80A AT

33KV)

TOTAL LOAD DUE TO GUINESS SUBSTATION = 246.7A AT 33KV

TOTAL LOAD DUE TO GUINESS SUBSTATION = 13.8MW

CURRENT IN SECTION 1 = 576.7A

IMPEDANCE OF SECTION 1 = (0.0022 +j0.2) x 8 = ( 0.0176 + j1.6)Ω

AT FULL LOAD VOLTAGE DROP OF SECTION 1 = I x Z = 576.7X

(0.0176+j1.6) = (10.14 +j921.6) V

CURRENT IN SECTION 2 AT FULL LOAD = 330A

IMPEDANCE OF SECTION 2 = (0.002+j0.2) x 6 = (0.012+j1.2) Ω

VOLTAGE DROP IN SECTION 2 AT FULL LOAD = 330 x (0.012+j1.2)Ω =

(3.96 + j396)V

TOTAL VOLTAGE DROP = VOLTAGE DROP IN SECTION 1 + VOLTAGE

DROP IN SECTION 2 = (14.1 + j1317.6) V

|V| =1.32KV

76

VOLTAGE AT THE RECEIVING END = 33-1.32= 31.68KV

VOLTAGE REGULATION = RECEIVING END VOLTAGE x 100 SENDING END VOLTAGE

= 31.68 x 100 = 96 % 33.0

3.1.1.2 CALCULATIONS FOR 11KV FEEDERS

3.1.1.2.1 UGBOWO 11KV FEEDER

RATED CURRENT CAPACITY = 401.9A

% LOADING = 350 X 100 = 87.1% 401.9

TOTAL LINE RESISTANCE = (0.0024 +j0.395) x 20.5 = (0.0492 + j8.096)Ω

VOLTAGE DROP = I x Z = 350 x ( 0.0492 + j8.096) = (17.22 + j2833.6)V |V| =2.83KV

VOLTAGE AT THE MOST REMOTE END OF FEEDER= 8.17KV

TOTAL OUTAGE PERIOD = 302+ 61 + 120 + 270 + 242 + 352 = 134MINUTES

TOTAL SERVICE PERIOD = 44640MINUTES

AVAILABILITY = 44640 -1347 = 0.97 44640

3.1.1.2.2 FEDERAL GOVERNMENT COLLEGE 11KV FEEDER

RATED CURRENT CAPACITY OF LINE = 401.9A

% LOADING OF LINE = 110 X 100 = 27.3% 401.9

TOTAL LINE IMPEDANCE = (0.0024 +j0.395) x 7 = (0.0168 +j2.765)Ω

VOLTAGE DROP = I X Z = 110 X(0.0168 + j2.765) = (1.848 +j304.15)V

|V| = 0.3KV

77

VOLTAGE AT THE MOST REMOTE END =11-0.3=10.7KV

TOTAL OUTAGE PERIOD = 53 + 46 + 181 +170 +54 =504MINS

TOTAL SERVICE PERIOD = 44640MINS

AVAILABILITY = ACTUAL PERIOD FEEDER WAS IN SERVICE TOTAL SERVICE PERIOD

AVAILABILITY = 44640 – 504 = 0.99 44640

3.1.1.2.3 EGUADIEKEN 11KV FEEDER


%LOADING OF LINE = 180 x 100 = 44.8% 401.9

TOTAL LINE IMPEDANCE = (0.0024 + j0.395) x 9 = (0.022 + j3.56)

VOLTAGE DROP = I X Z = 180 X (0.022 + j3.56) = (3.96 +j640.8) V

|V| =0.64KV

VOLTAGE AT THE MOST REMOTE END = 11.0 – 0.64 = 10.38KV

TOTAL OUTAGE PERIOD = 692MINS



AVAILABILITY = 44640 – 692 = 0.99 44640

3.1.1.2.4 USELU 11KV FEEDER

78

% LOADING OF LINE = 350 X 100 = 87.1% 401.9TOTAL LINE IMPEDANCE = (0.0024 + j0.395) x 10 = (0.024 +j3.95) Ω

VOLTAGE DROP = I X Z = 350 X (0.024 +j3.95) V

|V| = 1.4KV

VOLTAGE AT THE MOST REMOTE SUBSTATION = 11.0 – 1.4 =9.6KV

TOTAL OUTAGE PERIOD: 180 + 190 + 132 + 189 + 30C 8 + 135 = 1134MINS.

TOTAL SERVICE PERIOD = 44640 MINS


AVAILABITY = 44640 – 1134 = 0.98

44640

3.1.1.3 TRANSFORMER LOADING Transformer 1

RATING: 15MVA, 33/11KV

COOLING TYPE: ONAN

WINDING TYPE: DY1

CALCULATIONS

MAXIMUM LOAD ON TRANSFORMER = 350 + 110 = 460A

P =√3xIxVxCosø

79

TRANSFORMER RATED CURRENT = 15 X 10 6 = 803.36A √3X11X103X0.98

%LOADING = 460 X 100 = 57.3% 803.36

MAXIMUM H.V VOLTAGE = 34.0KV (RECORDE BY OPERATORS)

MINIMUM H.V VOLTAGE = 31.04KV (FROM CALCULATIONS)

MAXIMUM L.V VOLTAGE = 11.3KV (RECORDE BY OPERATORS)

MINIMUM L.V VOLTAGE = 10.4KV (FROM CALCULATIONS)

3.1.1.3.2 TRANSFORMER 2


COOLING TYPE: ONAN

WINDING TYPE: DY1

CALCULATIONS

MAXIMUM LOAD ON TRANSFORMER = 180 + 350 = 530A

P =√3xIxVxCosø RATED FULL LOAD CURRENT = 15 X 10 6 = 803.36 √3X11X103X0.98

% LOADING = 530 X 100 = 66% 803.36 MAXIMUM H.V VOLTAGE =34.0KV

MINIMUM H.V VOLTAGE = 31.04KV

MAXIMUM L.V VOLTAGE = 11.3 KV

MINIMUM L.V VOLTAGE = 10.4KV

80

PROTECTION AVAILABLE FOR THE TRANSFORMERS

Differential protection

Over current protection

Restricted earth fault protection

Buchholz (gas) protection

Winding temperature protection

Surge protection

LINE PROTECTION

2-Phase over current relay

1-Sensitive earth fault relay

3.1.2 SILUKO 33/11KV INJECTION SUBSTATION


3.1.2.1.1 OLIHA 11KV FEEDER

% LOADING OF LINE: 360 X100 =89.57% 401.9

CALCULATIONS

TOTAL LINE IMPEDANCE= (0.0024 + j0.395) x 6 = (0.012 +j2.4)Ω

VOLTAGE DROP= IxZ= 360X(0.012 + j2.4)=(4.32 + j864)V

|V| =0.9KV

VOLTAGE AT THE MOST REMOTE END = 11-0.9=10.1KV

AVAILABILITY = ACTUAL PERIOD FEEDER WAS IN SERVICE TOTAL SERVICE PERIODTOTAL SERVICE PERIOD: 44640 MINUTES

81

AVAILABILITY= 44640-2147 = 0.9544640

3.1.2.1.2 UPPER SILUKO 11KV FEEDER

% Loading of line = 240 x 100 =59.72% 401.9

TOTAL LINE IMPEDANCE =(0.0024 + j0.395) X 8 =(0.0192 + j3.16)Ω

VOLTAGE DROP = I x Z = 240 x(0.0192 + j3.16) =(4.608 + j758.4) 1.7 KV

|V| = 0.76KV

VOLTAGE AT THE MOST REMOTE END OF THE LINE =11-0.76=10.4KV

TOTAL OUTAGE PERIOD = 996 MINS



AILABILITY = 44640 – 996 =0.98 44640

3.1.2.1.3 EDO TEXTILE MILL 11KV FEEDER

% LOADING OF LINE: 290 X 100 =72.2% 401.9TOTAL LINE IMPEDANCE = (0.0024 + j0.395) x 6.1 = (0.015 + j2.41)

VOLTAGE DROP = I X = 290 X (0.015 + j2.4) = (4.35 + j696)

|V| = 0.7KV

VOLTAGE AT THE REMOTE END OF FEEDER = 11-0.7=10.3KV

TOTAL OUTAGE PERIOD: 3056 MINUTES

82

SERVICE PERIOD: 44640MINUTES


AVAILABILITY =44640– 3056 =0.93 44640

3.1.2.1.4 UWELU 11KV FEEDER

% LOADING OF LINE: 320 X 100 =77.9% 401.9 TOTAL LINE IMPEDANCE :( 0.0024 + j 0.395) X 8 = (0.019 + j3.16)Ω

VOLTAGE DROP : I X Z = 320 X(0.019 + j3.16) = (6.08 + j1011.2)Ω

|V| = 1.0KV

TOTAL OUTAGE PERIOD: 1349MINUTES

SERVICE PERIOD: 44640MINS


AVAILABILITY= 44640 – 1349 = 0.97 44640

3.1.2.2 TRANSFORMER LOADING

Transformer 1

RATING: 15 MVA, 33/11KV

COOLING TYPE: ONAN

WINDING TYPE: DY11

CALCULATIONS

COMBINED LOAD ON TRANSFORMER: 600A

83

P =√3xIxVxCosø

RATED FULL LOAD CURRENT: 803.6A

% LOADING 600 X 100 =74.7% 803.6


RATING: 15MVA,33/11KV

COOLING TYPE: ONAN

WINDING TYPE:DY11

CALCULATIONS

COMBINED LOAD: 610A

P =√3xIxVxCosø

TRANSFORMER RATED CURRENT= 803.36A

% LOADING OF TRANSFORMER = 610 X 100 = 76% 803.36







84

Surge protection

LINE PROTECTION



3.1.3 WELFARE 33/11KV INJECTION SUBSTATION 3.1.3.1 CALCULATIONS FOR 11KV FEEDERS

UPPER SAKPONBA FEEDER

% LOADING OF LINE = 440 X 100 =109.5% 401.9TOTAL LINE IMPEDANCE = (0.0024 + j0.395) X7 =(0.016 +j2.765)Ω

VOLTAGE DROP = I X Z = 440 X(0.016 + j2.765) =(7.04 + j1216.6)V

|V| =1.2KV

VOLTAGE AT REMOTE END = 11-1.2 = 10.8KV




AVAILABILITY = 44640 – 1116 = 0.98 44640

3.1.3.1.2 ST. SAVIOUR 11KV FEEDER

% LOADING OF LINE = 70 X 100 = 17.4% 401.9

TOTAL LINE IMPEDANCE = (0.0024 + j0.395) X 3 = (0.0072 + j1.185) Ω

85

VOLTAGE DROP = I X Z = 70 X (0.0072 + j1.185)V

|V| = 0.1KV

VOLTAGE AT REMOTE END = 11-0.1=10.9KV


SERVICE PERIOD: 44640


AVAILABILITY= 44640 – 1349 = 0.97 44640



COOLING TYPE: ONAN

WINDING TYPE : DY11

CALCULATIONS

MAXIMUM LOAD = 440+70 = 510A

P =√3xIxVxCosø

RATED CURRENT = 803.36A

% LOADING = 510 X 100 =63.5% 803.36



86





Surge protection

LINE PROTECTION



3.1.4 GUINESS 33/11/6.6KV INJECTION SUBSTATION


CALCULATIONS

TOTAL LINE IMPEDANCE = (0.0022 + j0.22) x 8 =(0.0176 +j1.76)Ω

MAXIMUM LOAD DUE TO 11KV FEEDERS = 270 + 230 = 500A

87

EQUIVALENT LOAD AT 33KV = 500 X 11 = 166.7A 33MAXIMUM LOAD DUE TO 6.6KV FEEDER = 400A

EQUIVALENT LOAD AT 33KV = 400 X 6.6 = 80A 33

LOAD DUE TO GUINESS SUBSTATION AT 33KV =66.7+ 80=246.7A

LOAD DUE TO UGBOWO SUBSTATION AT 33KV = 330A

TOTAL LOAD FLOWING THROUGH THE 8KM SECTION AT PEAK

PERIOD =330 +246.7 =576.7A

VOLTAGE DROP = I X Z = 576.7 x (0.0176+ j1.6) =(10.14 + j921.6)V

|V| = 0.92KV


3.1.4.2.1 NEW BENIN 11 KV FEEDER

CALCULATIONS

% LOADING OF LINE = 270 X 100 = 67.2% 401.9TOTAL LINE IMPEDANCE= (0.0024 + j0.395) x 7=(0.0168 + j2.765)Ω

VOLTAGE DROP = 270 X (0.0168 + j2.765) =(4.54 + j746.6)V

|V| =0.8KV TOTAL SERVICE PERIOD = 44640MINUTES

TOTAL OUTAGE PERIOD = 385 MINUTES


AVAILABILITY = 44640 – 385 = 0.99 44640

88

3.1.4.2.2 BDPA 11KV FEEDER

CALCULATIONS

% LOADING = 230 X 100 = 70.3% 401.9

TOTAL LINE IMPEDANCE = (0.0024+ j 0.395) x 4 = (0.0096 + j1.58) Ω

VOLTAGE DROP = I X Z = 230 X(0.0096 + j1.58) = (2.208 + j363.4)V

|V| =0.36KV

3.1.4.2.3 ASABA 6.6 KV FEEDER

CALCULATIONS

% LOADING OF LINE = 400 X 100 = 59.7% 670

TOTAL LINE IMPEDANCE = (0.0024 + j0.395) x 7 = (0.0168 + j2.77) Ω

VOLTAGE DROP = I XZ = 400 X(0.0168 + j2.77) = (6.72 + j1108)V

|V| = 1.1KV

TOTAL OUTAGE PERIOD = 1563MINUTES

TOTAL SERVICE PERIOD = 44640MINUTES


AVAILABILITY = 44640 – 1563 = 0.97 44640

3.1.4 .3 TRANSFORMER LOADING

89

3.1.4.3.1 Transformer 1

CALCULATIONS

COMBINED LOAD = 270 + 230 = 500A

P =√3xIxVxCosø

RATED CURRENT CAPACITY = 15 X 10 6 = 803.365 √3 X 11 X 103 X 0.98

% LOADING = 500 X 100 = 62.2% 803.36


CALCULATIONS

MAXIMUM LOAD ON TRANSFORMER = 400A

P =√3xIxVxCosø TRANSFORMER RATED CURRENT= 7.5 X 106 = 669.5A √3 X 6.6 X 103 X0.98

% LOADING OF TRANFORMER = 400 X 100 = 59.8% 669.5







90

Surge protection

LINE PROTECTION



3.1.5 NEKPENEKPEN 33/11KV INJECTION SUBSTATION


3.1.5.1.1 FEEDER 1

CALCULATIONS

TOTAL OUTAGE PERIOD:

135+71+175+76+124+66+25+51+199+3810+210+20+180+165+63=5370MINS

TOTAL SERVICE PERIOD: 44640MINS


AVAILABILITY= 44640-5370 =0.88 44640

3.1.5.1.2 FEEDER 2

CALCULATIONS

TOTAL OUTAGE

PERIOD:15+116+126+70+195+64+375+24+49+75+200+45=1354MINUTES

TOTAL SERVICE PERIOD= 44640


91

AVAILABILITY= 44640-1354 =0.97 44640

3.1.5.1.3 FEEDER 3

CALCULATIONS


TOTAL SERVICE PERIOD: 44640


AVAILABILITY= 0.97

3.1.5.1.4 FEEDER 4

TOTAL OUTAGE PERIOD=688MINUTES

TOTAL SERVICE PERIOD=44640MINUTES

AVAILABILITY = ACTUAL PERIOD FEEDER WAS IN SERVICE TOTAL SERVICE PERIODAVAILABILITY=0.98

3.1.5.2 TRANSFOMER LOADING


TRANSFORMER RATED FULL LOAD CURRENT= 803.36A

%LOADING= 800 X 100 = 99.96% 803.36


92

RATED CURRENT = 803.36A% LOADING = 630 X 100 =78.4% 803.36







Surge protection

LINE PROTECTION



3.1.6 ETETE 33/11KV INJECTION SUBSTATION


CALCULATIONS

MAXIMUM LOAD AT 11KV= 432 + 264+ 440+316 = 1452A

TRANSFORMER RATIO: 33/11 = 3:1

MAXIMUM LOAD AT 33KV = 1452 = 484A 3VOLTAGE DROP = I X Z = 484 X (00616 + j0.56)V

93

|V| = 0.3KV 3.1.6.2 CALCULATIONS FOR 11KV FEEDERS 3.1.6.2.1 IHAMA 11KV FEEDER

% LOADING OF LINE = 432 X 100 = 107.5% 401.9TOTAL LINE IMPEDANCE = (0.0024 + j 0.395) X 5 = (0.0120 + j 1.975)Ω

VOLTAGE DROP = I X Z = 432 X(0.0120 = j 1.975)V

|V| = 0.9KV


TOTAL SERVICE PERIOD: 44640MINUTES


AVAILABILITY = 44640 – 2120 = 0.95 44640

3.1.6.2.2 DUMEZ 11KV FEEDER

% LOADING OF LINE = 264 X 100 = 65.7% 401.9

TOTAL LINE IMPEDANCE = (0.0024 + j0.395) x 6 = (0.0144 + j2.4)Ω

VOLTAGE DROP = 264 X (0.0144 + j2.4) = (3.80 + j625.7)V | V| = 0.63KV

3.1.6.2.3 UGBOR 11 KV FEEDER

% LOADING OF LINE: 440 X 100 = 109.5% 401.9

TOTAL LINE IMPEDANCE :( 0.0024 +j 0.395) X 6 = (0.0144 + j2.37) Ω

VOLTAGE DROP = I X Z = 440 X(0.0144 + j2.37)V

|V| =1.04KV

TOTAL OUTAGE PERIOD = 866MINUTES

TOTAL SERVICE PERIOD= 44640MINUTES

AVAILABILITY = ACTUAL PERIOD FEEDER WAS IN SERVICE

94

TOTAL SERVICE PERI AVAILABILITY = 44640 – 866 = 0.98

44640

3.1.6.2.4 UPPER SAPELE 11KV FEEDER

% LOADING OF LINE = 316 X 100 = 78.6% 401.9

TOTAL LINE IMPEDANCE = (0.0024 + j0.395) X 7 = (0.0168 + j2.765)Ω

VOLTAGE DROP = I X Z = 316 X (0.0168 + j2.765)V

|V| = 0.9KV




AVAILABILITY = 44640 – 1305 = 0.97 44640



COMBINED LOAD: 696A

P =√3xIxVxCosø

I = 803.36A

% LOADING = 696 X 100 = 86.7% 803.36


95

COMBINED LOAD = 756A

P =√3xIxVxCosø

I = 15 X 10 6 = 803.36 √3x11x103x0.98

% LOADING OF TRANSFORMER = 756 x 100 = 94.1% 803.36

3.1.7 GRA 33/11KV INJECTION SUBSTATION

3.1.7.1 CALCULATIONS FOR 11KV

3.1.7.1.1 OBA PALACE 11KV FEEDER

CALCULATIONS

TOTAL OUTAGE PERIOD: 114+55=169MINUTES


AVAILABILITY=44640-169 44640

AVAILABILITY=0.99

3.1.7.1.2 GRA 11KV FEEDER

CALCULATIONS


TOTAL OUTAGE PERIOD= 19+265+25+165+66= 540MINS

TOTAL SERVICE PERIOD=44640MINS

AVAILABILITY= 44640-540 = 0.98 44640

96

3.1.7.1.3 RESERVATION 11KV FEEDER

TOTAL OUTAGE PERIOD: 60MINS

TOTAL SERVICE PERIOD: 44640MINS

AVAILABILITY= 44640-60 44640



I= 15x10 6 √3x11x103x0.98

I= 803.36A

The full load current rating of the transformer=803.6A

MAXIMUM LOAD RECORDED ON THE TRANSFORMER=564A

% LOADING= 564 x 100 = 70.2% 803.36


Transformer rated maximum load= 803.36A

% LOADING= 430 X 100 =53.5% 803.36

3.1.8 EVBUOTUBU 33/11KV INJECTION SUBSTATION

3.1.8.1 CALCULATIONS FOR 11KV FEDERS

97

3.1.8.1.1 EVBUOTUBU 11KV FEEDER

CALCULATIONS

%LOADING OF LINE = 288 X 100 = 71.7% 401.9

TOTAL LINE IMPEDANCE= (0.0024 + j 0.395) X 7 = (0.0168 + j2.8)Ω

VOLTAGE DROP = I X Z =288 X(0.0168 + j2.8) = (4.8 + j2.8)V

|V| = 0.8KV




AVAILABILITY = 44640 -931 = 0.98 44640

3.1.8.1.2 ASORO 11KV FEEDER

CALCULATIONS

%LOADING OF LINE =255 X 100 = 63.5% 401.9

TOTAL LINE IMPEDANCE = (0.0024 + j0.395) X 8 = (0.019 + j 3.16)Ω

VOLTAGE DROP = I XZ = 255 X (0.019 + j 3.16) = (4.9 + j805)V

|V| =0.8KV

98

CALCULATIONS




AVAILABILITY = 44640 – 810 = 0.98 44640

3.1.8.2 TRANSFORMER LOADING MAXIMUM LOADING = 543A

P =√3xIxVxCosø

RATED MAXIMUM CURRENT = 803.36A

% LOADING = 543 X 100 = 67.6% 803.36

3.1.9 FEDERAL SECRETERIAT 33/11KV INJECTION

SUBSTATION

3.1.9.1 CALCULATIONS FOR 11KV FEEDERS 3.1.9.1.1 NEW AUCHI 11KV FEEDER

CALCULATIONS

% LOADING OF LINE = 440 X 100 =109.5% 401.9

99

TOTAL LINE IMPEDANCE = (0.0024 + j0.395) X 6 = (0.0144 + j2.37) Ω

VOLTAGE DROP = I X Z = 440 X(0.0144 + j2.37) = (6.34 + j1042.8)V

|V| = 1.04KV

TOTAL OUTAGE PERIOD = 90+240+300+60+4=694MINS

TOTAL SERVICE PRIOD = 44640MINS

AVAILABILITY = ACTUAL PERIOD FEEDER WAS IN SERVICE

TOTAL SERVICE PERIOD

AVAILABILITY = 44640 – 694 = 0.99 44640

3.1.9.1.2 FEDERAL HOUSING 11KV FEEDER

CALCULATIONS

% LOADING OF LINE = 180 X 100 = 44.8% 401.9

TOTAL LINE IMPEDANCE = (0.0024 + j 0.395) X 4 =(0.0096 + j1.58)Ω

VOLTAGE DROP = 180 x (0.0096 + j1.587) = (1.728 + j284.4)V

|V| =0.3KV TOTAL OUTAGE PERIOD = 120+105+60+185 = 470 MINS



AVAILABILITY = 44640 – 470 = 0.99 44640 3.1.9.2 TRANSFORMER LOADING

TRANSFORMER1 RATED CURRENT = 803.36A

% LOADING = 620 X 100 = 77.2% 803.36

100

TRANSFORMER 2

MAXIMUM LOAD = 190 + 110 = 300A

P =√3xIxVxCosø


% LOADING = 300 X 100 = 37.3% 803.36

3.1.10 IKPOBA DAM 33/11KV INJECTION SUBSTATION 3.1.10.1 CALCULATIONS ON 11KV FEEDERS

3.1.10.1.1 DAM 11KV FEEDER

CALCULATIONS

% LOADING OF LINE = 200 X 100 = 49.8% 401.9

TOTAL LINE IMPEDANCE = (0.0024 + j0.395) X0.1 = (0.00024 + j 0.0395)Ω

VOLTAGE DROP = 200 X (0.00024 + j 0.0395) = (0.048 + j79)V

| V| =0.08KV




AVAILABILITY = 44640 – 110 = 0.98 44640

101

3.1.10.1.2 UPPER LAWANI 11KV FEEDER

CALCULATIONS

% LOADING OF LINE = 110 X 100 = 27.4% 401.9

TOTAL LINE IMPEDANCE = (0.0024 + j0.395) x 4 = (0.0096 + j1.58)Ω

VOLTAGE DROP = I X Z = 110 x (0.0096 + j1.58) = (1.056 + j173.8)V

|V| = 0.2KV




AVAILABILITY = 44640- 795 = 0.98 44640

3.1.10.1.3 OKHORO 11KV FEEDER

% LOADING = 190 X 100 = 47.3% 401.9

TOTAL LINE IMPEDANCE =(0.0024 +j 0.395) X 4.5 = (0.0108 + j1.8)Ω

VOLTAGE DROP = I x Z =190 x (0.0108 + j1.8)= (2.052 + j337.7)V

|V| =0.34KV TOTAL OUTAGE PERIOD = 549MINS

TOTAL SERVICE PERIOD = 44640


AVAILABILITY = 4640 4-549 = 0.99

102

44640



MAXIMUM LOAD = 200A

P =√3xIxVxCosø


% LOADING = 200 X 100 = 49.1% 401.7


MAXIMUM LOAD = 190 + 110 = 300A

P =√3xIxVxCosø


% LOADING = 300 X 100 = 37.3% 803.36

3.2.0 SUBSTATIONS IN DELTA ENVIRONMENTS

3.2.1 OGHAREKI 33/11KV INJECTION SUBSTATION

3.2.1.1 CALCULATIONS ON 11KV FEEDERS

3.2.1.1.1 OGHAREKI 11KV FEEDER

CALCULATIONS

RATED CURRENT CAPACITY =401.9A

103

% LOADING OF LINE = 400 X 100 = 68.8% 401.9

TOTAL LINE IMPEDANCE=(0.0024+j0.395) x 10 = (0.024 + j3.95)Ω

VOLTAGE DROP = I X Z = 450 X(0.024 +j3.95)V = (10.8 +j1777.5)V

|V|=1.8KV

VOLTAGE AT THE MOST REMOTE SUBSTATION =11 – 1.8 = 9.2KV

CALCULATIONS:

TOTAL OUTAGE PERIOD: 15+40+25=80mins.

TOTAL SERVICE PERIOD: 31x24x60=44640mins

Availability of feeder= (44640-80)/44640 =0.99


I=P/ √ 3xVx COSø = (15x106)/√3x11x103x0.98

Full load current = 803.36A

Maximum load recorded on the transformer =450A

3.2.2 OGHAREFE 33/11KV INJECTION SUBSTATION

3.2.2.1 CALCULATIONS ON 11KV FEEDERS 3.2.2.1.1 GOVERNOR 11KV FEEDER

CALCULATIONS


% LOADING OF LINE = 220 X 100 = 54.7% 401.9

104

TOTAL LINE IMPEDANCE =(0.0024 +j 0.395) X 6 =(0.0144 +j2.37)Ω

VOLTAGE DROP = I XZ = 220 X(0.0144 +j2.37) = (3.16 +j521.4)

|V| = 0.52KV

VOLTAGE AT THE MOST REMOTE SUBSTATION = 11 – 0.52 =10.48KV

No outage was recorded on the feeder in the month of May 2007. The availability

of the feeder is unity.

3.2.2.1.2 OTEFE 11KV FEEDER

CALCULATIONS


% LOADING OF LINE = 300 X 100 = 74.7% 401.9

TOTAL LINE IMPEDANCE=(0.0024 + j0.395) x 10 =(0.024+j3.95)Ω

VOLTAGE DROP = I X Z = 300 X(0.024 + j3.95) =(7.2 +j1185)

|V| = 1.2KV Total outage period = 526mins

Total period in the month = 44640mins

Availability = (44640-526)/44640 =0.98


P = √3xIxVxCosø

Full load current = (15x106)/ (√3x11x103x0.98) = 803.36A

% Loading of transformer = 520/803.36 x100 =64.7%

105

PROTECTION AVAILABLE IN THE SUBSTATION

TRANSFORMER PROTECTION

1. Differential protection

2. Over current protection

3. Restricted earth fault protection

4. Buchholz (gas) protection

5. Winding temperature protection

6. Surge protection

LINE PROTECTION

1.Over current relays

2.Earthfault relays

3.2.3 BETA GLASS 33/11KV INJECTION SUBSTATION


3.2.3.1.1 UGHELLI 11KV FEEDER

CALCULATIONS

106


% LOADING = 200 X 100 = 48.7% 401.9 AVAILABILITY = ACTUAL PERIOD FEEDER WAS IN SERVICE TOTAL SERVICE PERIOD

No. of days in May=31

No. of hours in a day=24

No. of minutes in one hour=60

Total period of time in one month=31x24x60=44640

Period feeder was off service=275+22+21=318minutes

AVAILABILITY= (44640-318)/44640 =0.99

3.2.3.1.2 BETA GLASS 11KV FEEDER


% LOADING = 150 X 100 = 36.5 % 401.9

TOTAL LINE IMPEDANCE = (0.0024 + j 0.395) X 3 = (0.0072 + j1.185)Ω

VOLTAGE DROP = I X Z = 150 X (0.0072 + j1.185) = (1.05 +j177.8)V

|V| = 0.2KV


Availability = (44640-22) /44640 =0.99

Ughelli 11kv feeder: 200A

Beta glass 11kv feeder: 150A

Total: 350A

107

Rating of transformer: 7.5MVA

Cooling type: ONAF

Winding type: Yd11

CALCULATIONS

P = √3xIxVxcos

P=Power=7.5MVA

I=current

V=Voltage=11kv

Cosø=power factor=0.98

I= p/ (√3V cosø) = (7.5x106) / (√3x11x103x0.98) =401.68A

The substation is capable of supplying 401.68A

There is therefore, a reserve capacity of 401.68-350=51.68A

Percentage loading of the transformer = (350/401.68) x100 =87.13%

CHAPTER FOURSUMMARY AND DISCUSSION

TABLE 4.1 TABULATED SUMMARY OF 11KV FEEDERS

SUBSTATION FEEDER

LENGTH (KM)

CAPACITY (A)

MAX.LOAD(A)

%LOADING

NOMINALVOLTAGE (KV)

VOLTAGE DROP

(KV)%VOLTAGE REGULATION

AVAILABILITY

REMARKS

WELFARE

ST.SAVIOUR 3.0 401.9 70 17.4 11 0.10 0.9 0.97 SATISFACTORY

“ UPPER SAKPONBA

7.0 401.9 440 109.5 11 1.2 0.9 0.98 LINE IS OVER LOADED

GUINESS

NEW BENIN 8.0 401.9 270 67.2 11 0.8 7.2 0.99 SATISFACTORY

“ BDPA 4.0 401.9 230 70.3 11 0.36 3.3 0.97 SATISFACTORY“ ASABA 7.0 670.0 400 59.7 6.6 1.10 10.0 0.97 HIGN LOSSES

108

NEKPENEKPEN

FEEDER 1 7.0 401.9 350 87.1 11 0.17 1.6 0.88 SATISFACTORY

“ FEEDER 2 6.0 401.9 400 99.5 11 0.95 0.64 0.97 SATISFACTORY“ FEEDER 3 6.0 401.9 410 102.0 11 0.98 8.9 0.97 LINE IS OVER

LOADED“ FEEDER 4 7.1 401.9 220 54.7 11 0.62 5.6 0.98 SATISFACTORY

ETETE

IHAMA 5.0 401.9 432 107.5 11 0.90 8.2 0.95 LINE IS OVER LOADED

“ DUMEZ 6.0 401.9 264 65.7 11 0.63 5.7 N/A SATISFACTORY“ UGBOR 6.0 401.9 440 109.5 11 1.04 9.5 0.98 LINE IS OVER

LOADED“ UPPER SAPELE 7.0 401.9 316 78.6 11 0.90 8.2 0.97 SATISFACTORY

GRA OBA PALACE 7.0 401.9 285 70.9 11 0.78 7.1 0.99 SATISFACTORY“ GRA 6.0 401.9 279 69.4 11 0.67 6.1 0.98 SATISFACTORY“ RESERVATION 6.0 803.6 330 53.5 11 1.0 9.1 0.99 SATISFACTORY

EVBUOTUBU

EVBUOTUBU 8.0 401.9 288 71.7 11 0.8 7.3 0.98 SATISFACTORY

“ ASORO 8.0 401.9 255 63.5 11 0.8 7.3 0.98 SATISFACTORYFEDERA

L SECRETERIAT

NEW AUCHI 6.0 401.9 440 109.5 11 1.04 9.5 0.99 LINE IS OVER LOADED

“ FEDERAL HOUSING

4.0 401.9 180 44.8 11 0.3 2.7 0.99 SATISFACTORY

IKPOBA DAM

DAM 0.1 401.9 200 49.8 11 0.08 0.7 0.98 SAT SATISFACTORY ISFACTORY

“ UPPER LAWANI

4.0 401.9 110 27.4 11 0.2 1.8 0.98 SATISFACTORY

“ OKHORO 4.5 401.9 190 47.3 11 0.34 3.1 0.99 SATISFACTORYUGBOW

OUGBOWO 20.5 401.9 350 87.1 11 2.83 2.83 0.97 SATISFACTORY

“ FEDERAL GOVERNMENT

COLLEGE

7.0 401.9 110 27.3 11 1.9 1.9 0.99 SATISFACTORY

“ EGUADIAEKEN 9.0 401.9 180 44.8 11 0.64 0.64 0.99 SATISFACTORY“ USELU 10.0 401.9 350 87.1 11 1.4 1.4 0.98 SATISFACTORY

OGHAREKI

OGHAREKI 10.0 401.9 400 99.8 11 1.8 1.8 0.99 SATISFACTORY

OGHAREFE

GOVERNOR 6.0 401.9 220 54.7 11 0.52 0.52 1.0 SATISFACTORY

“ OTEFE 10.0 401.9 300 74.7 11 1.2 1.2 0.98 SATISFACTORYBETA

GLASSUGHELLI 12.0 401.9 200 48.7 11 0.95 0.95 0.99 SATISFACTORY

“ BETA GLASS 3.0 401.9 150 36.5 11 0.2 0.2 0.99 SATISFACTORYSILUKO OLIHA 6.0 401.9 360 89.57 11 0.9 0.9 0.95 SATISFACTORY

“ UPPER SILUKO 8.0 401.9 240 59.72 11 0.76 0.76 0.98 SATISFACTORY“ EDO TEXTILE

MILL6.1 401.9 290 72.2 11 0.7 0.7 0.93 SATISFACTORY

“ UWELU 8.0 401.9 320 77.9 11 1.0 1.0 0.97 SATISFACTORY

TABLE 4.2: TABULATED SUMMARY OF TRANSFORMERSSUBSTATION INSTALLED

CAPACITY(MVA)

MAX.LOAD

T1(A)

MAX.LOAD

T2(A)

%LOADING

T1

%LOADING

T2

%VOLTAGE

REGULATIONT1

%VOLTAGE

REGULATIONT2

REMARKS

UGBOWO 2X15 460 530 57.3 66.O 7.96 7.96 SATISFACTORYSILUKO 2X15 600 610 74.7 76.0 5.3 5.3 SATISFACTORYWELFARE 1X15 510 N/A 63.5 N/A 5.3 N/A SATISFACTORYGUINESS 1X15

1X7.5500 400 62.2 59.8 5.3 5.9 SATISFACTORY

NEKPENEKPEN 2X15 800 630 99.6 78.4 8.9 8.9 SATISFACTORYETETE 2X15 696 756 86.7 94.1 2.6 2.6 SATISFACTORYGRA 2X15 564 430 70.2 53.5 8.7 8.7 SATISFACTORYEVBUOTUBU 1X15 543 N/A 67.6 N/A 1.8 N/A SATISFACTORYFEDERAL SECRETERIAT

1X15 620 N/A 77.2 N/A 2.7 N/A SATISFACTORY

109

IKPOBA DAM 1X7.51X15

200 300 49.1 37.3 8.7 8.7 SATISFACTORY

OGHAREKI 1X15 450 N/A 56.1 N/A 2.7 N/A SATISFACTORYOGHAREFE 1X15 220 N/A 27.4 N/A 2.7 N/A SATISFACTORYBETA GLASS 1X7.5 350 N/A 87.1 N/A 2.7 N/A SATISFACTORY

DISCUSSION

The availability of the 11KV feeders and the injection substations was observed

to be quite low in some cases. This can be attributed to overloaded transformers

and poor distribution network.

It was also observed that feeders were taken off service due to poor generated

power.

The common denominators to all the substations in this study are:

All the substations have outdoor 33KV switchgear and indoor 11KV

switchgear.

All the transformers belong to the ONAN cooling system. It is highly

recommended that for the transformers to carry higher load especially in

overloaded substations, assisted cooling in the form of fans should be

provided.

In some substations with two transformers, it was observed that their

vector groups are dissimilar making it impossible to run them in parallel.

No frequency meter was found in any of the control rooms. This leads to

slow response to system disturbances and eventually lead to system

collapse.

110

It was observed that a 33/6.6KV transformer is in circuit at GUINNES

substation in Benin City. This should be upgraded to take care of the

overload and voltage drop problem being encountered by consumers on

that transformer.

Transformers were observed to have tripped on high winding temperature

on many occasions. This can be prevented if the temperature warning

alarms are made effective.

REFERENCES

Brown R.E (2002) “Electric Power Distribution Reliability” “Marcel Dekker, Inc. New York.

Billinton, R and Allan, R.N (1996) “Reliability Evaluation of Power Systems”. Platinum Press, New York, USA.

GEC –ALSTHOM (2004) ‘‘Network Protection and Automation Guide’’ ‘‘GEC- ALSTHOM, United Kingdom’’

111

Power Holding Company of Nigeria Hourly Reading Sheets and operational records.

112

performance characteristics of-main

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